Demonstration of ATP-dependent, ubiquitin-conjugating activities in higher plants
Ubiquitin is a 76 amino acid eucaryotic polypeptide with several important functions that arise from its ability to become covalently ligated to other cytoplasmic and nuclear proteins. Ubiquitin has recently been purified from higher plants and found to be very homologous, both structurally and functionally, to the highly conserved animal form. Here, the authors present evidence that crude extracts from several plants have the capacity to conjugate ubiquitin to other plant proteins using either labelled human or oat ubiquitin as a substrate. The reaction requires ATP and can be detected in soluble extracts from dry seeds, etiolated shoots and green leaves, with etiolated shoot extracts having the highest activity. Mixing experiments indicate that the low activity found with green tissue in vitro is the result of an endogenous inhibitor. The conjugating activities are extremely labile with a half-life of 20 min at 30/sup 0/C. The addition of polyphenol inhibitors fails to protect the system from this inactivation. In addition to conjugating activities, crude plant extracts also have ATP-independent activities that degrade ubiquitin conjugates. These results provide the first evidence that higher plants contain the necessary enzymes for ubiquitin conjugate formation. Further analysis of these activities should help clarify the functions of ubiquitination in plants.
- Research Organization:
- Univ. of Wisconsin, Madison
- OSTI ID:
- 5097056
- Report Number(s):
- CONF-8606151-; TRN: 86-034837
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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POLYPEPTIDES
BIOCHEMICAL REACTION KINETICS
ATP
BIOLOGICAL HALF-LIFE
IODINE 125
LEAVES
MAN
OATS
SEEDS
SUBSTRATES
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
CEREALS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GRASS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PEPTIDES
PLANTS
PRIMATES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques